The present invention relates to pigment compositions and coating compositions that are used to prepare pigmented coatings that exhibit geometric metamerism or metallic flop, wherein the hue of the coating changes based on the viewing angle of the observer. The invention is based on the general discovery that the flop of a pigmented coating is greatly enhanced if it is colored with a pigment composition that contains a small particle size pigment that is treated with a small mount of a copper phthalocyanine, indanthrone or carbazole dioxazine compound which acts as a flop-enhancing agent.
The use of small particle size pigments as transparent pigments in coating compositions is well-known in the art. Coating compositions containing transparent pigments are useful for automotive and industrial finishes.
Copper phthalocyanine, indanthrone and carbazole dioxazine compounds are also well-known in the art, primarily as pigments or as dyes. However, their use as flop-enhancing agents has not previously been reported.
U.S. Pat. No. 5,362,780 describes pigment compositions containing a 2,9-dichloroquinacridone and a blue-colored copper phthalocyanine sulfonic acid or indanthrone sulfonic acid. The copper phthalocyanine and indanthrone sulfonic acids are utilized to adjust the color of the magenta 2,9-dichloroquinacridone pigment in order to obtain a heat-stable violet pigment which is used for coloring engineering plastics. The compositions in the '780 patent are not utilized in coating compositions, and there is no suggestion that the copper phthalocyanine and indanthrone sulfonic acids could enhance the flop of pigmented coatings.
According to the present invention, a pigment composition containing a small particle size pigment and a flop-enhancing agent is utilized to pigment a coating composition. The pigmented coatings prepared from such coating compositions exhibit a high degree of flop which represents an improvement in the art and which permits access to new color space regions.